DESCRIPTION: Appropriate sensitivity and response to the transmitter glutamate is essential for normal CNS function. Glutamate is the main excitatory transmitter in the CNS and an important trophic factor during neuronal development. We have shown that exposure to alcohol during development alters the response of immature CNS neurons to glutamate receptor agonists. We will now examine this action of alcohol in detail, to gain a more complete understanding of alcohol's effects on developing CNS neurons and to identify the site and mechanisms of alcohol s actions. The neuronal response to glutamate involves multiple receptor subtypes and transduction mechanisms, including mechanisms linked to intracellular Ca2+ signaling. Our studies will focus on this aspect of the response to glutamate because of the importance of Ca2+ as a second messenger and because Ca2+ plays an essential role in normal neuronal development. Moreover, excess Ca2+ is known to be neurotoxic. Therefore, alcohol induced alterations in Ca2+ signaling could significantly alter neuronal development. Few studies have examined the effects of alcohol on Ca2+ signaling in either immature or mature neurons. Therefore, our work should contribute significantly to this area. The Ca2+ signals will be measured with microscopic video imaging techniques and the Ca2+ sensitive dye fura-2. This technique will enable an assessment of alcohol s effects on both somatic and dendritic pathways. The dendritic region is of particular interest, because it is the site of synaptic input mediated by glutamate. To identify the site and mechanisms of alcohol action, pharmacological manipulation of Ca2+ signaling pathway components will be used. Parallel electrophysiological studies will be carried out as well, since membrane potential changes are intimately linked to Ca2+ signaling pathways. Mature and immature neurons will be studied, to distinguish effects of alcohol unique to developing neurons and to determine if alcohol s effects represent permanent alterations or a more temporary adjustment that could recover after alcohol removal. A CNS neuronal type known to be sensitive to alcohol and used in previous studies, the cerebellar Purkinje neurons, will be the experimental model. These neurons will be grown in modified organotypic cultures that simulate the in vivo environment. This preparation offers technical advantages for physiological experimentation and permits control over alcohol exposure and other variables. Results from these studies should contribute significantly to our understanding of the alternations in glutamatergic synaptic function caused by alcohol exposure to the developing nervous system.